I. Field of the Invention
The present invention is directed to a percutaneous access device adapted to be implanted within a patient on a long-term basis.
II. Description of the Related Art
Percutaneous access devices (hereinafter PAD) are employed to provide a through-the-skin coupling or connection between an organ or device implanted within the human body and some external device as, for example, to introduce or withdraw fluids from the patient's body or to establish electrical or pneumatic connections to an implanted device, such as a dynamic aortic patch of the type disclosed in U.S. Pat. No. 4,630,597. The PAD must protrude through the skin and, as set forth in more detail in U.S. Pat. No. 4,634,422, a primary concern is that of preventing the development of infection which is prone to occur at the opening in the skin through which the device projects. U.S. Pat. No. 4,634,422 is directed to a PAD and implanting technique which achieves a firm bond between the underlying dermal layer of the skin and the projecting portion of the PAD to prevent down growth of the epidermal layer of the skin to prevent marsupialization of the PAD and to prevent sinus tract formation caused by epidermal cell proliferation. The PAD of U.S. Pat. No. 4,634,422 includes a removable sleeve which, when assembled on the PAD, forms that portion of the external surface of the projection which passes through the dermal layer. In preparation for implantation, this sleeve is removed from the PAD and its external surface is formed, by nuclear bombardment, with a plurality of tiny pores. A coating of dermal cells is then cultured on this porous surface by techniques described in U.S. Pat. No. 4,634,422, this dermal cell coating growing into the pores of the sleeve surface to firmly mechanically bond the coating to the sleeve surface. Upon reassembly of the sleeve on the PAD and implantation of the PAD into the patient, the dermal cells of the patient will bond to those of the dermal cell coating on the sleeve within a relatively short time to form a barrier layer, preventing down growth of the epidermis along the side of the sleeve.
While the PAD and implantation techniques described in U.S. Pat. No. 4,634,422 present several major advantages over prior art devices, the sleeve employed is of a rigid material. In those applications where the PAD was employed as a plug-in connector to external, electrical or pneumatic devices, rigidity of the projecting portion of the PAD was, to some extent, desirable. However, rigidity of the projecting portion of the PAD made it more likely that tearing of the bond between the PAD and dermal layer would occur if the projecting portion of the PAD or external leads connected to it were inadvertently struck or displaced relative to the skin as by an involuntary movement of the patient.
Forming of the projecting portion of the PAD of a relatively soft, resilient material was not thought practical for several reasons. First, suitable biocompatible materials of sufficient softness and resiliency, if constructed as the sleeve of the PAD of U.S. Pat. No. 4,634,422, would be extremely difficult to handle and manipulate after the dermal layer cell had been cultured on the sleeve, particularly in the step of assembling the sleeve upon the PAD. Second, such materials were found to be very poorly adapted to the formation of microscopic pores of the desired diameter, depth and density, at least by economically feasible techniques. Third, construction of the PAD as a one-piece member, to avoid the first problem referred to above, seemed to require the culturing of a dermal layer over a far larger area of the PAD than would be necessary.
The present invention is directed to a PAD especially designed to be constructed from a soft, resilient material upon which microscopic pores for bonding a layer of dermal cells to the external surface of the PAD may be formed over a minimum area no larger than that essentially required. The PAD is also constructed to minimize displacement of the PAD relative to the patient's skin by movement of external leads or conduits connected to or passing through the PAD.